HBO’s third season of “Girls” ended on a cliffhanger with Lena Dunham’s character debating whether to leave Brooklyn — and soul mate Adam — for the University of Iowa Writers’ Workshop.

Well, thanks to a careless casting director who was openly reading a script for the 2015 season in a crowded New York subway car for all to see — spies got sneak peeks at scenes from the upcoming Season 4 and can confirm that Hannah does indeed head to the Midwest.

“We all know in the Season 3 finale that Lena’s character gets into Iowa, but we didn’t know if she’d really go,” said one source who saw the script and confirmed that scenes next season are set in Iowa.

“In one of the scenes, Jessa (Jemima Kirke) and Shoshanna (Zosia Mamet) are FaceTiming with Hannah (Dunham), and they’re in New York while she’s living in Iowa City.”

Actresses Jemima Kirke and Lena Dunham.Photo: Splash News

The show’s Season 3 finale aired March 23. Filming for Season 4 just began in New York with Dunham spotted filming around town in her signature shorty shorts with co-stars Kirke, Mamet, Allison Williams and Adam Driver.

There have been rumors that series creator Dunham’s courting Taylor Swift for a guest role.

Meantime, the script that was visible on the subway ride to multiple fans had a giant watermark with a casting agent’s name, Tony Behringer, of Central Casting. According to IMDb, Behringer has cast extras in “Girls” as well as the upcoming Jennifer Aniston/Owen Wilson indie movie, “Squirrels to the Nuts,” Clint Eastwood’s movie version of the hit musical “Jersey Boys” and Kevin Costner’s “Draft Day.”

The University of Iowa reportedly denied a request by the show to shoot on its campus, but one of the show’s directors has hinted that scenes for the new season will be filmed elsewhere in Iowa City. An HBO rep told us: “We cannot confirm any plot points or story lines…just because a scene may be set in Iowa doesn’t mean the cameras are actually in Iowa.” The cable network’s “Boardwalk Empire” has set scenes from Chicago to Ireland without leaving town.